1. Field of the Invention
This invention relates to detecting electrical characteristics of a read head and more particularly relates to measuring the dampening of cleaning brush bristles in contact with the read head within a tape drive system.
2. Description of the Related Art
Recording and playback systems for magnetic mediums are subject to degradation during use as a result of the accumulation of debris which occurs on the magnetic transducer heads of such systems. Transducer heads include magnetic read/write heads and associated read/write elements. Hence, there is a need to periodically clean the magnetic transducer heads. Accordingly, there exist several techniques for cleaning a magnetic transducer head.
One technique utilizes a separate, dedicated “cleaning cartridge” to perform periodic cleaning of the recording transducer. A “cleaning cartridge” contains a supply of unrecorded abrasive tape that is used to clean one or more magnetic transducer heads. For example, the recording heads found on a tape drive can be cleaned with a “cleaning cartridge.” In order to utilize a “cleaning cartridge,” the recording or playback of the medium must be stopped, the data cartridge removed, and the “cleaning cartridge” inserted. The “cleaning cartridge” is then run within the record or playback system so as to clean the recording transducer. Once cleaning is complete, the “cleaning cartridge” is removed, and a data cartridge is reinserted. However, after the “cleaning cartridge” has been used, a new data cartridge may be loaded into the system in order to evaluate the performance of the magnetic transducer head so as to confirm that cleaning has been successfully completed.
Where magnetic recording/playback system is a tape recording/playback system, the cleaning cartridge includes an abrasive cleaning tape that can cause excessive tape head wear on the magnetic head. The abrasiveness of the cleaning tape can be adjusted in order to tailor its effectiveness. If the cleaning tape is made sufficiently effective to thoroughly remove debris, then the cleaning tape should only be used when it is necessary; otherwise, excessive magnetic head wear will result. Such a problem can occur where a piece of abrasive cleaning tape is provided as a leader on a data tape cartridge such that each time a tape is used the leader is used to clean a read/write head. Furthermore, the provision of an abrasive tape leader within a data tape cartridge eventually results in degradation of the abrasive leader from debris accumulating on the cleaning tape. If the abrasive cleaning tape is effective to thoroughly remove debris from a magnetic head, then a routine must be established to limit use of the cleaning tape only when it is necessary.
Where magnetic tape is used to store computer data, the presence of errors represents a significant problem even if the errors occur infrequently. In certain applications, the loss of data requires that a user be able to perform a cleaning operation in response to recognized drop-out errors, but does not immediately prevent use of the equipment prior to cleaning. In some cases, the loss of a single bit of computer data can be of significant importance, and recovery from such an error must be done in a manner that ensures error-free data storage and retrieval. While error correction is possible via error algorithms, data loss can still present problems to a user.
One form of magnetic storage comprises existing linear and helical scan tape drives that are used for storage and retrieval of computer data. Such tape drives use a single reel in the form of a magnetic tape cartridge to house the magnetic tape media. A special leader or leader block is attached to the magnetic tape media at one end which enables the tape drive to extract the magnetic tape from the magnetic tape cartridge.
“Tape recorder” as used herein refers to one form of magnetic recording/playback system comprising magnetic tape transcription equipment. Such equipment is understood to include standard tape recorders having fixed or movable heads, as well as accurate scan and helical scan transcription equipment as is typically used in analog and digital tape recorders. According to one implementation, a linear transcription head is employed, although the present invention has application in other tape recording environments. As described here, “transcription” is intended to mean read and/or write operations that are performed with a tape recorder, and is not intended to be limited to a particular use or format for data.
Another conventional technique is found on a typical helical scan tape drive wherein a head cleaning device is built into a mechanism of the tape drive. More particularly, a helical scan tape drive forms a recording method that is used on videotape and digital audio tape (DAT) that runs the tracks diagonally from top to bottom in order to increase the storage capacity. A drum containing read/write heads is used to read/write information in diagonal segments from/onto a segment of magnetic tape. A head cleaner is located on an opposite side of the drum than the tape. In this manner, while data is being written/read, the head cleaner can be concurrently cleaning the heads as they pass by on the drum.
One linear tape drive which does have a head cleaner built into the tape drive mechanism is the International Business Machines (IBM) Magstar 3590. The IBM Magstar 3590 has a cleaning brush built into the tape drive mechanism such that the cleaning brush is brought into contact with the read/write heads during a tape threading operation. More particularly, as a leader block on a data tape is pulled back into the tape cartridge, the leader block triggers a lever which engages the brush against the read/write heads. An actuator moves the heads up and down in order to provide scrubbing action between the brush and heads. Generally, there is not a way to determine how well the brush is operating without removing physically examining the brush. In certain tape drives a switch is attached at the arm of the brush to provide notification to a user that the brush may be inoperative. However, the switch does not detect the quality of connection or contact between the brush and the heads. For example, if the bristles on the brush were non-existent, the switch would not detect this error as long as the brush arm activated at the appropriate time.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that determines contact between a brush and magnetic head(s) without additional hardware being required. Additionally, the need exists for an apparatus, system, and method that possesses the increased ability to measure the contact of the brush bristles against the magnetic head during a cleaning operation. Beneficially, such an apparatus, system, and method would allow a user to configure a contact threshold that, if satisfied, the user is notified that a brush and/or brush arm is inoperative and needs to be replaced.